Railway wheels are generally either wrought or cast steel, and despite strict quality control measures, may contain flaws resulting from the manufacturing process. These flaws can potentially include voids, cracks, as well as inclusions, which can weaken the wheel and potentially lead to wheel failure. Ultrasound testing has been commonly employed to detect such flaws.
Railway wheels ultrasonically analyzed by fixed position transducers typically examine the wheel and its underlying structure only at discrete, single locations around the perimeter of the wheel tread face or wheel flange. To obtain a more complete diagnostic analysis of the entire wheel structure, without the intensive analysis required by a fixed position transducer, an automated ultrasonic testing method has been developed.
Automated ultrasonic testing has been challenged, to some extent, by the size and weight of railway wheels (typically weighing from 700 to 1000 pounds) which can make the automated collection of accurate ultrasonic test data difficult. Particularly problematic are railway wheels with dimensional tolerances that, although within an acceptable range for production purposes, hamper the automated collection of accurate test data.
In prior art test fixtures, the typical railway wheel may have dimensional tolerances capable of producing dynamic instabilities as the wheel is rotationally driven for ultrasonic examination. These instabilities result in the deflection of the wheel from axial centerline rotation around the geometric center of the wheel in the test fixture. This has proven problematic as the collection of accurate ultrasonic test data often requires maintaining a stable geometric orientation as the wheel rotates.